This invention relates to electrophotographic printing, and more specifically to diagnostic operation of electrophotographic printers.
Special service and diagnostic programs are stored and used on many printer marking engines to assist the field engineer in the correct and efficient troubleshooting of the marking engine and its subsystems. All these programs are designed and implemented to minimize the total service time. Minimizing the total service time minimizes the cost of service to the service organization as well as the loss in productivity to the owner of the equipment. Special service and diagnostic routines for the electrophotographic image formation and image development process are especially valuable, since this multi-step process conditions the photosensitive receiver electrically, making visual inspection under ambient light impossible. Paper handling problems and others, by contrast, can be observed and corrected using ambient lighting.
This invention facilitates identification of the root causes of, and the particular rotating member responsible for, image artifacts visible in the printed output of an electrophotographic printer. The program of the invention establishes a special operating mode for the marking engine, referencing the printing process intentionally to each rotating member of the electrophotographic process in turn. The referencing insures that image artifacts and/or non-uniformities originating from each rotating member are visible in the same location on each printed output. Since the rotating members employed are intentionally designed to be different in diameter, the special program according to this invention es the printing process to each one of the rotating members in conjunction with variable receiver sizes, enabling an operator to associate each image artifact or non-uniformity with a specific rotating member causing it. The invention""s special operating mode enhances the appearance of image artifacts through zero offset voltage printing and flat-field exposure of the rotating member images as appropriate. Where referencing of the printing process cannot be done, the invention prints master timing marks on the rotating member images to guide the image interpretation.
The invention""s special printing mode is necessarily avoided during normal print production so that image variations and/or artifacts are never in the same location on each printed output, the non-uniform wear of rotating members is minimized, and the useful life of such components is effectively extended.